From 45b5a04393fcd5517463a5caebf10b74d5a976ec Mon Sep 17 00:00:00 2001
From: Ben Adams <thundercat@illyriad.co.uk>
Date: Mon, 8 Apr 2019 17:34:07 +0100
Subject: [PATCH] Move enumerating extra headers to separate method (#7706)

---
 .../Core/src/Internal/Http/HttpResponseHeaders.cs    | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/Servers/Kestrel/Core/src/Internal/Http/HttpResponseHeaders.cs b/src/Servers/Kestrel/Core/src/Internal/Http/HttpResponseHeaders.cs
index 02d8a36cd2..1e24c07178 100644
--- a/src/Servers/Kestrel/Core/src/Internal/Http/HttpResponseHeaders.cs
+++ b/src/Servers/Kestrel/Core/src/Internal/Http/HttpResponseHeaders.cs
@@ -30,9 +30,17 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
         internal void CopyTo(ref BufferWriter<PipeWriter> buffer)
         {
             CopyToFast(ref buffer);
-            if (MaybeUnknown != null)
+
+            var extraHeaders = MaybeUnknown;
+            if (extraHeaders != null && extraHeaders.Count > 0)
             {
-                foreach (var kv in MaybeUnknown)
+                // Only reserve stack space for the enumartors if there are extra headers
+                CopyExtraHeaders(ref buffer, extraHeaders);
+            }
+
+            static void CopyExtraHeaders(ref BufferWriter<PipeWriter> buffer, Dictionary<string, StringValues> headers)
+            {
+                foreach (var kv in headers)
                 {
                     foreach (var value in kv.Value)
                     {